The WHO said it was working closely with Congo authorities to help deploy health workers and protective equipment in the remote area, which is difficult for teams to access, in order to "rapidly control the outbreak".

The organisation underlined the importance of tracing people who had contact with confirmed victims to prevent the disease spreading.

Sufferers are advised to keep themselves isolated while awaiting treatment for a disease whose incubation period is 21 days.

The outbreak could test a recently developed experimental ebola vaccine that WHO says could be used in emergencies.

The global vaccine alliance GAVI said 300,000 doses are available "if needed to stop this outbreak becoming a pandemic."

So far all the cases have been tied to a remote village, and it's a strain of ebola that's been seen in the country before.

Dr. Allarangar Yokouide, the WHO representative in Congo, said the first teams of specialists should arrive in the affected area of Likati on Saturday.

The zone is some 1300km from the capital, Kinshasa.

"The area in Likati is difficult to access, but the work of tracing contacts is very crucial to stopping the epidemic in its tracks," he said.

The community is near the border with Central African Republic.

Ebola occasionally jumps to humans from animals including bats and monkeys.

The new cluster of Ebola cases will again test one of the world's least equipped health systems. The US Agency for International Development has said an estimated 70 per cent of the population has little or no access to health care.